This invention relates generally to cellular telephones and their power supplies. More particularly, the present invention relates to an emergency power supply contained within a cellular telephone, separate from the main battery, which can be activated for a temporary supply of power.
Cellular telephones typically have a main rechargeable battery, which can be comprised of a series of electrochemical cells in series or in parallel, and that main battery provides electricity to all functioning components of the cellular telephone. Once the main battery has discharged its energy, the cellular telephone can no longer send or receive transmissions. Most cellular telephones have a power level indicator or other warning method to alert the user of the cellular telephone of the remaining charge on the telephone and if a power failure is imminent.
However, the onset of the complete discharge of the main battery can occur very quickly when the cellular telephone is actively being used for communication. Furthermore, most charge warning indicators on cellular telephones do not indicate the amount of communication remaining that the main battery will support. Thus, the user may find a dead battery, which is a serious problem if that user then needs to make an emergency telephone call. If there is not another power source to either power the cellular telephone or recharge the discharged main battery, the cellular telephone will remain inoperative.
In electronic devices, it is known to provide an emergency power source to either power the device for a limited duration, or to power the device solely to keep data storage facilities (such a volatile memory) powered for the maintenance of the data. An example of short storage would be a universal power supply for a computer that provides reserve power to the computer after main power loss. The reserve power lasts long enough for a user to exit all critical operations before the computer stops running. An example of a battery backing up a specific function is the use of an alkaline or rechargeable battery in a bedside radio-alarm clock whereby the clock continues to keep time after the main power has ceased.
Accordingly, there is a need for an improved power supply to provide emergency power for electronic accessories.